Neuroprotective agents

ABSTRACT

Novel stereoisomers of GS-164 are provided. The compounds, such as (3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol (TH-237A) and (3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol (TH-242A) exhibit neuroprotective effects via a mechanism that does not involve microtubule stabilization.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority to U.S. ProvisionalApplication Ser. No. 60/732,074, filed on Nov. 1, 2005, which is herebyincorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Paclitaxel (Taxol®) is a therapeutic agent with antitumor activityagainst ovarian, breast, and lung carcinomas. The compound is extractedfrom the bark of the Pacific yew tree Taxus brevifolia, as well as fromneedles and stems of this and other Taxus species, and its complexchemical structure has been determined. Interest in this compound arisesfrom not only its clinical activity against poorly responsive solidtumors but also from its unique mechanism of action. Paclitaxel promotestubulin polymerization and stabilizes microtubules that result in theinhibition of cell migration and chromosome segregation by blocking thetransit of cycling cells in the G2/M phase. More recently, paclitaxelhas been proposed as a therapeutic for stabilizing microbules in thebrain cells of individuals who are deficient in normal tau proteins, forexample in individuals suffering from Alzheimer's Disease. SeeTrojanowski et al., U.S. Pat. No. 5,580,898.

In 1997, a group of Japanese researchers described a novel smallsynthetic compound designated GS-164, which was reported to stimulatetubulin polymerization and stabilize microtubules. See Shintani et al.,GS-164, a small synthetic compound, stimulates tubulin polymerization bya similar mechanism to that of Taxol, Cancer Chemother Pharmacol40:513-520 (1997); Japanese Patent No. 8-325147 (1996). The researchersreported that GS-164 has activities similar to those of paclitaxel invitro and in vivo, even thought it was structurally unrelated. Thecompound was reported to stimulate tubulin polymerization with one-tenththe activity of paclitaxel. According to the authors, the stereoisomerof GS-164 that was responsible for its microtubule-stabilizing effectswas determined to be the R/R isomer, which mimicked the structure ofpaclitaxel.

R/R isomer GS-164 (Shintani 1997)(3R,5R)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol

Several years later, some of the present inventors conducted preliminarystudies on the effects of several purported microtubule stabilizingagents, including paclitaxel and GS-164, in beta amyloid induced celldeath in primary neurons. See Michaelis et al, Amyloid Peptide Toxicityand Microtubule-Stabilizing Drugs, Journal of Molecular Neuroscience,19, 101-105, (2002). The GS-164 used in these experiments was a mixtureof stereoisomers that had been produced according to Shintani (1997).

In the present invention, a novel stereoisomer of GS-164 denominatedTH-237A has been isolated, and it exhibits neuroprotective effects.Moreover, it was shown that this novel stereoisomer surprisingly doesnot stimulate tubulin polymerization as reported with respect to the(R/R) GS-164 stereoisomer. Moreover, the novel stereoisomer showssignificant uptake by the brain. Thus, the present invention is directedto novel compositions comprising substantially pure stereoisomers, aswell as methods of using these stereoisomers as neuroprotective agents.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed novel stereoisomers andstereomerically pure compounds. In one aspect, the stereoisomers havethe Formula I:

wherein A and B are sulfur or oxygen; wherein R₁ and R₂ areindependently halogen, alkyl, alkoxy, haloalkyl; and wherein R₃ isalcohol. It will be appreciated that R₁ and R₂ may independently be inthe para, meta, or ortho position.

In an preferred aspect, stereoisomers according to

are provided wherein R₁ and R₂ are independently halogen, alkyl, alkoxy,haloalkyl; and wherein R₃ is alcohol. For example, the inventivestereiosomers may be selected from(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A);(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A);(3R,5S,7as)-(3,5-bis(4-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(4-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.

In still another aspect, inventive stereoisomers are selected from thegroup consisting of(3R,5S,7as)-(3,5-bis(3-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(3-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.

In still another aspect, inventive stereoisomers are selected from thegroup consisting of(3R,5S,7as)-(3,5-bis(2-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(2-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.

The stereoisomers of the present invention are useful for treatingneurodegenerative disorders, such as amyloidosis disorders. In oneaspect, a method for treating a neurodegenerative disorder is providedwhich comprises administering to a patient in need of such treatment atherapeutically effective amount of a stereoisomer of the presentinvention. A preferred stereoisomer is(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) or(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A) or a prodrug thereof. The stereoisomers may be administeredparenterally, transdermally, mucosally, nasally, buccally, sublingually,or orally. In addition, the stereoisomers may be associated withpharmaceutically acceptable excipients. In one aspect, the stereoisomersare complexed with a cyclodextran (e.g. Captisol®).

The stereoisomers of the present invention also surprisingly do notstabilize microtubules, as evidenced by tubulin centrifugation assays,multi-well plate assays, and/or cold stability experiments discussedherein. For example, in one aspect, the compounds of the presentinvention promote less than about 20%, 10%, or 5% of tubulinpolymerization at a 200 μM concentration using the tubulin assemblycentrifugation assay. In another aspect, the stereoisomers of thepresent invention are two, three, or four times less potent thanpaclitaxel in promoting tubulin polymerization when using a multi-wellplate assay. In still another aspect, cold stability experiments showthat the stereoisomers of the present invention prevent depolymerizationonly about 20, 10 or 5% of microtubules at concentrations around 400 μM

In still another aspect, the stereoisomers of the present invention areshown not to inhibit tubulin polymerization as evidenced byradiolabeling the compounds, competitive binding, and/or immunostainingas discussed herein.

Additional aspects of the invention, together with the advantages andnovel features appurtenant thereto, will be set forth in part in thedescription which follows, and in part will become apparent to thoseskilled in the art upon examination of the following, or may be learnedfrom the practice of the invention. The objects and advantages of theinvention may be realized and attained by means of the instrumentalitiesand combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) is an ellipsoid drawing of the molecular structure of TH-237Aand TH-236B (one enantiomer shown) from x-ray diffraction studies. FIG.1(B) is an ellipsoid drawing of the molecular structure of TH-242A andTH-242B (one enantiomer shown) from x-ray diffraction studies.

FIG. 2 shows the dose-dependent effects of TH-237A on survival ofprimary cortical neurons exposed to the toxic Aβ peptide for 48 hours.The % neurons surviving was determined by the Live/Dead assay. Data arefrom 6 randomly selected fields from 2 neuronal preparations (n=˜1,500cells/condition). Statistical significance was determined by Students ttest. #=p<0.001 for controls vs Aβ only. **=p<0.001 for Aβ only vs Aβ+.

FIG. 3 shows the effects of TH-237A on toxicity induced by diversestimuli. Primary neurons were exposed to 100 nM staurosporine (Str,),100 nM Thapsigargin (Tg), 25 μM paraquat (PQ), or 25 μM hydrogenperoxide (H₂O₂) with and without 100 nM TH-237A. Mean % survival wasdetermined 24 hours later, and statistical significance was assessedusing Student's t test. *=p<0.05 and **=p<0.005 for each toxic stimulusalone vs the toxic stimulus plus the drug. Data are from about 1,000cells per condition.

FIG. 4 shows the pharmacokinetic properties of TH-237A followed inplasma and the brain. Male Balb/C mice were dosed with TH-237A (10mg/kg) via either an i.v. injection into the tail vein (filled squares)or via subcutaneous (sc) injection (open squares). At indicated times,12 mice (n=6, i.v.; n=6, s.c.) were anesthetized with isoflurane andblood collected via cardiac puncture. Mice were perfused with 30 mL ofsaline and brain tissue harvested. TH-237A in plasma (left axis) andbrain (right axis) was quantified using mass spectrometric methods.

FIG. 5 is an immunoblot of abnormal tau labeled with AT8 antibodies. Theblot shows representative data from 2 different animals in each group.In addition, a non-transgenic, wild-type mouse that does not have anyhyperphosphorylated tau is shown.

FIGS. 6(a)-(c) quantifies the P3 fraction labeling with antibodies AT8,Cp13, and PHF1 from P3 fractions from the brain. The data are mean +/−SE(+Tau=5 mice, Tau/FR=7 mice, Tau/FR/Drug=7 mice).

FIGS. 7(a)-(c) quantifies the P3 fraction labeling with antibodies AT8,Cp13, and PHF1 from P3 fractions from the spinal cord. The data are mean+/− SE(+Tau=2 mice, Tau/FR =7 mice, Tau/FR/Drug=7 mice).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The present invention is directed to novel stereoisomers having theFormula I:

wherein A and B are sulfur or oxygen; wherein R₁ and R₂ areindependently halogen, alkyl, alkoxy, haloalkyl; and wherein R₃ isalcohol. R₁ and R₂ may independently be in the para, meta, or orthoposition.

A preferred composition comprises stereomerically pure(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) or stereomerically pure(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A). The composition preferably substantially free of(3R,5R)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanoland(3S,5S)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol.The compositions are useful as neuroprotective agents, and in thetreatment of neurodegenerative disorders.

Further, the invention includes the use of stereomerically pure(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol (TH-237A), incombination with one or more other therapeutic agents for the treatmentof a neurodegenerative disorder, including, but not limited to thoseinvolving beta amyloids. The compositions administered in each of thesemethods may be concurrent, sequential, or in any combination ofconcurrent or sequential.

Further, the invention includes the use of stereomerically pure(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol (TH-242A), incombination with one or more other therapeutic agents for the treatmentof a neurodegenerative disorder, including, but not limited to thoseinvolving beta amyloids. The compositions administered in each of thesemethods may be concurrent, sequential, or in any combination ofconcurrent or sequential.

As used herein, the term “alkyl” embraces branched or unbranchedsaturated hydrocarbon group of one to 10 carbon atoms, such as methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl,and the like. “Lower alkyl” refers to an alkyl group of one to six, morepreferably one to four, carbon atoms.

The term “alkoxy” embraces oxy-containing groups substituted with analkyl group. Examples include, without limitation, methoxy, ethoxy, andtert-butoxy. Most preferred are “lower alkoxy” groups having one to sixcarbon atoms. Examples of such groups include methoxy, ethoxy, propoxy,butoxy, isopropoxy, and tert-butoxy.

As used herein, the term “alcohol” embraces an alkyl group having one ormore hydroxy (—OH) substituents. Primary, secondary, and tertiaryalcohols are contemplated, such as mono-alcohols as well as polyhydroxyvariants. Preferred alcohols are those containing from about one up tosix carbon atoms. Exemplary of preferred aliphatic alcohols are:methanol, ethanol, 1-propanol, 2-propanol, 1-propen-2-ol, 1-butanol,2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, and3-methyl-1-butanol. Of the alcohols, methanol is most preferred.

As used herein, the term “halo” or “halogen” embraces to fluoro, chloro,bromo, or iodo, usually regarding halo substitution for a hydrogen atomin an organic compound. Of the halogens, fluorine is the most preferred.

As used herein, the term “haloalkyl” refers to an alkyl group having atleast one halogen thereon. The term includes monohaloalkyl, dihaloalkyl,and trihaloalkyl groups. Examples of haloalkyl groups includefluoromethyl, difluoromethy, trifluoromethyl, fluoroethyl,pentafluoroethyl, 2,2,2-trifluoroethyl, and 2,2,3,3,3-pentafluoropropyl.Preferably, the haloalkyl comprises trifluoromethyl.

As used herein, the term “stereoisomers” is a general term for allisomers of individual molecules that differ only in the orientation oftheir atoms in space. The term includes enantiomers anddiastereoisomers. The term “diastereoisomers” refers to stereoisomersthat are not mirror images of one another, while the term “enantiomers”refers to stereoisomers that are mirror images of each other and arenonsuperimposeable.

The term “stereomerically pure” refers to a composition that comprisesone stereoisomer of a compound and is substantially free of otherstereoisomers of that compound. For example, a stereomerically purecomposition of a compound having one chiral center will be substantiallyfree of the opposite enantiomer of the compound. A stereomerically purecomposition of a compound having two chiral centers will besubstantially free of other diastereoisomers of the compound. A typicalstereomerically pure compound comprises greater than about 80% by weightof one stereoisomer of the compound and less than about 20% by weight ofother stereoisomers of the compound, more preferably greater than about90% by weight of one stereoisomer of the compound and less than about10% by weight of the other stereoisomers of the compound, even morepreferably greater than about 95% by weight of one stereoisomer of thecompound and less than about 5% by weight of the other stereoisomers ofthe compound, and most preferably greater than about 97% by weight ofone stereoisomer of the compound and less than about 3% by weight of theother stereoisomers of the compound. In a preferred aspect, thestereomerically pure compounds preferably have none of the (R/R)stereoisomer or the (S/S) stereoisomer.

The term “racemic” refers to a mixture of equal parts of enantiomers andwhich is optically inactive. For example, TH-236B comprises a racemicmixture of the (R/R) and (S/S) enantiomers.

The term “neuroprotection” refers to inhibition of progressivedeterioration of neurons that leads to cell death.

The term “neurodegenerative disorder” refers to a disorder in whichprogressive loss of neurons occurs either in the peripheral nervoussystem or in the central nervous system. Examples of neurodegenerativedisorders include, but are not limited to chronic neurodegenerativediseases such as diabetic peripheral neuropathy, Alzheimer's disease,Pick's disease, diffuse Lewy body disease, progressive supranuclearpalsy (Steel-Richardson syndrome), multisystem degeneration (Shy-Dragersyndrome), motor neuron diseases including amyotrophic lateral sclerosis(“ALS”), degenerative ataxias, cortical basal degeneration,ALS-Parkinson's-Dementia complex of Guam, subacute sclerosingpanencephalitis, Huntington's disease, Parkinson's disease, multiplesclerosis, synucleinopathies, primary progressive aphasia, striatonigraldegeneration, Machado-Joseph disease/spinocerebellar ataxia type 3 andolivopontocerebellar degenerations, Gilles De La Tourette's disease,bulbar and pseudobulbar palsy, spinal and spinobulbar muscular atrophy(Kennedy's disease), primary lateral sclerosis, familial spasticparaplegia, Wernicke-Korsakoff's related dementia (alcohol induceddementia), Werdnig-Hoffmann disease, Kugelberg-Welander disease,Tay-Sach's disease, Sandhoff disease, familial spastic disease,Wohifart-Kugelberg-Welander disease, spastic paraparesis, progressivemultifocal leukoencephalopathy, and prion diseases (includingCreutzfeldt-Jakob, Gerstmann-Straussler-Scheinker disease, Kuru andfatal familial insomnia). Other conditions also included within themethods of the present invention include age-related dementia and otherdementias, and conditions with memory loss including vascular dementia,diffuse white matter disease (Binswanger's disease), dementia ofendocrine or metabolic origin, dementia of head trauma and diffuse braindamage, dementia pugilistica and frontal lobe dementia. Also otherneurodegenerative disorders resulting from cerebral ischemia orinfaction including embolic occlusion and thrombotic occlusion as wellas intracranial hemorrhage of any type (including, but not limited to,epidural, subdural, subarachnoid and intracerebral), and intracranialand intravertebral lesions (including, but not limited to, contusion,penetration, shear, compression and laceration). Thus, the term alsoencompasses acute neurodegenerative disorders such as those involvingstroke, traumatic brain injury, schizophrenia, peripheral nerve damage,hypoglycemia, spinal cord injury, epilepsy, and anoxia and hypoxia.

Preferably, the neurodegenerative disorder is selected from Alzheimer'sdisease, Parkinson's disease, amyotrophic lateral sclerosis, age-relatedmemory loss, senility and age-related dementia, most preferably, theneurodegenerative disorder is Alzheimer's disease. Because, mostpreferably, the neurodegenerative disorder is Alzheimer's disease, alsodefined as an amyloidosis, other conditions within the methods of thepresent invention include other amyloidosis disorders which sharefeatures including, but not limited to, hereditary cerebral angiopathy,nonneuropathic hereditary amyloid, Down's syndrome, macroglobulinemia,secondary familial Mediterranean fever, Muckle-Wells syndrome, multiplemyeloma, pancreatic- and cardiac-related amyloidosis, chronichemodialysis arthropathy, and Finnish and Iowa amyloidosis.

As used herein and unless otherwise indicated, the term “prodrug” meansa derivative of a compound that can hydrolyze, oxidize, or otherwisereact under biological conditions (in vitro or in vivo) to provide thecompound of the present invention. For example, the compounds of thepresent invention encompass esters which may be hydrolyzed to thecorresponding alcohols. A thorough discussion is provided in T. Higuchiand V. Stella, Prodrugs as Novel Delivery Systems, Vol. 14 of the A.C.S.Symposium Series and in Edward B. Roche, ed., Bioreversible Carriers inDrug Design, American Pharmaceutical Association and Pergamon Press,1987, both of which are incorporated by reference herein.

The term “treating”, as used herein generally means that the compoundsof the invention can be used in humans or animals with at least atentative diagnosis of disease. The compounds of the invention willdelay or slow the progression of the disease thereby giving theindividual a more useful life span.

The term “preventing” as used herein means that the compounds of thepresent invention are useful when administered to a patient who has notbeen diagnosed as possibly having the disease at the time ofadministration, but who would normally be expected to develop thedisease or be at increased risk for the disease. The compounds of theinvention will slow the development of disease symptoms, delay the onsetof disease, or prevent the individual from developing the disease atall. Preventing also includes administration of the compounds of theinvention to those individuals thought to be predisposed to the diseasedue to age, familial history, genetic or chromosomal abnormalities,and/or due to the presence of one or more biological markers for thedisease.

Compositions of the Present Invention

The present invention contemplates compositions comprising thesubstantially pure stereoisomers disclosed herein. Preferably, thesecompositions include pharmaceutical compositions comprising atherapeutically effective amount of one or more of the substantiallypure stereoisomers along with a pharmaceutically acceptable carrier.

As used herein, the term “pharmaceutically acceptable carrier” means anon-toxic, inert solid, semi-solid liquid filler, diluent, encapsulatingmaterial, formulation auxiliary of any type, or simply a sterile aqueousmedium, such as saline. Some examples of the materials that can serve aspharmaceutically acceptable carriers are sugars, such as lactose,glucose and sucrose, starches such as corn starch and potato starch,cellulose and its derivatives such as sodium carboxymethyl cellulose,ethyl cellulose and cellulose acetate; powdered tragacanth; malt,gelatin, talc; excipients such as cocoa butter and suppository waxes;oils such as peanut oil, cottonseed oil, safflower oil, sesame oil,olive oil, corn oil and soybean oil; glycols, such as propylene glycol,polyols such as glycerin, sorbitol, mannitol and polyethylene glycol;esters such as ethyl oleate and ethyl laurate, agar; buffering agentssuch as magnesium hydroxide and aluminum hydroxide; alginic acid;pyrogen-free water; isotonic saline, Ringer's solution; ethyl alcoholand phosphate buffer solutions, as well as other non-toxic compatiblesubstances used in pharmaceutical formulations. Preferred carriers arecyclodextrins, such as Captisol®, and those described in U.S. Pat. Nos.6,046,177; 5,874,418; 5,376,645; and 5,134,127, which are incorporatedby reference.

Wetting agents, emulsifiers and lubricants such as sodium lauryl sulfateand magnesium stearate, as well as coloring agents, releasing agents,coating agents, sweetening, flavoring and perfuming agents,preservatives and antioxidants can also be present in the composition,according to the judgment of the formulator. Examples ofpharmaceutically acceptable antioxidants include, but are not limitedto, water soluble antioxidants such as ascorbic acid, cysteinehydrochloride, sodium bisulfite, sodium metabisulfite, sodium sulfite,and the like; oil soluble antioxidants, such as ascorbyl palmitate,butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT),lecithin, propyl gallate, aloha-tocopherol and the like; and the metalchelating agents such as citric acid, ethylenediamine tetraacetic acid(EDTA), sorbitol, tartaric acid, phosphoric acid and the like.

By a “therapeutically effective amount” or simply “effective amount” ofan active compound, is meant a sufficient amount of the compound totreat or alleviate the negative effects of a neurological disorder orneurodegenerative disease at a reasonable benefit/risk ratio applicableto any medical treatment. It will be understood, however, that the totaldaily usage of the active compounds and compositions of the presentinvention will be decided by the attending physician within the scope ofsound medical judgment. The specific therapeutically effective doselevel for any particular patient will depend upon a variety of factorsincluding the disorder being treated and the severity of the disorder;activity of the specific compound employed; the specific compositionemployed; the age, body weight, general health, sex and diet of thepatient; the time of administration, route of administration, and rateof excretion of the specific compound employed; the duration of thetreatment; drugs used in combination or coinciding with the specificcompound employed; and like factors well known in the medical arts.

The total daily dose of the active compounds of the present inventionadministered to a subject in single or in divided doses can be inamounts, for example, from about 0.1 to 100 mg/kg body weight or moreusually from 1 to 10 mg/kg body weight. Single dose compositions maycontain such amounts or submultiples thereof to make up the daily dose.In general, treatment regimens according to the present inventioncomprise administration to a human or other mammal in need of suchtreatment from about 1 mg to about 1000 mg of the active substance(s) ofthis invention per day in multiple doses or in a single dose of from 1mg, 5 mg, 10 mg, 100 mg, 500 mg or 1000 mg.

In certain situations, it may be important to maintain a fairly highdose of the active agent in the blood stream of the patient,particularly early in the treatment. Hence, at least initially, it maybe important to keep the dose relatively high and/or at a substantiallyconstant level for a given period of time, preferably, at least aboutsix or more hours, more preferably, at least about twelve or more hoursand, most preferably, at least about twenty-four or more hours.

The compounds of the present invention may be administered alone or incombination or in concurrent therapy with other agents which affect thecentral or peripheral nervous system, particularly selected areas of thebrain.

Liquid dosage forms for oral administration may include pharmaceuticallyacceptable emulsions, microemulsions, solutions, suspensions, syrups andelixirs containing inert diluents commonly used in the art, such aswater, isotonic solutions, or saline. Such compositions may alsocomprise adjuvants, such as wetting agents; emulsifying and suspendingagents; sweetening, flavoring and perfuming agents.

Injectable preparations, for example, sterile injectable aqueous oroleaginous suspensions may be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation may also be a sterile injectablesolution, suspension or emulsion in a nontoxic parenterally acceptablediluent or solvent, for example, as a solution in 1,3-butanediol. Amongthe acceptable vehicles and solvents that may be employed are water,Ringer's solution, U.S.P. and isotonic sodium chloride solution. Inaddition, sterile, fixed oils are conventionally employed as a solventor suspending medium. For this purpose any bland fixed oil can beemployed including synthetic mono- or diglycerides. In addition, fattyacids such as oleic acid are used in the preparation of injectables.

The injectable formulation can be sterilized, for example, by filtrationthrough a bacteria-retaining filter, or by incorporating sterilizingagents in the form of sterile solid compositions, which can be dissolvedor dispersed in sterile water or other sterile injectable medium justprior to use.

In order to prolong the effect of a drug, it is often desirable to slowthe absorption of a drug from subcutaneous or intramuscular injection.The most common way to accomplish this is to inject a suspension ofcrystalline or amorphous material with poor water solubility. The rateof absorption of the drug becomes dependent on the rate of dissolutionof the drug, which is, in turn, dependent on the physical state of thedrug, for example, the crystal size and the crystalline form. Anotherapproach to delaying absorption of a drug is to administer the drug as asolution or suspension in oil. Injectable depot forms can also be madeby forming microcapsule matrices of drugs and biodegradable polymers,such as polylactide-polyglycoside. Depending on the ratio of drug topolymer and the composition of the polymer, the rate of drug release canbe controlled. Examples of other biodegradable polymers includepolyorthoesters and polyanhydrides. The depot injectables can also bemade by entrapping the drug in liposomes or microemulsions, which arecompatible with body tissues.

Suppositories for rectal administration of the drug can be prepared bymixing the drug with a suitable non-irritating excrement, such as cocoabutter and polyethylene glycol which are solid at ordinary temperaturebut liquid at the rectal temperature and will, therefore, melt in therectum and release the drug.

Solid dosage forms for oral administration may include capsules,tablets, pills, powders, gelcaps, and granules. In such solid dosageforms the compounds may be admixed with at least one inert diluent suchas sucrose, lactose, or starch. Such dosage forms may also comprise, asis normal practice, additional substances other than inert diluents,e.g., tableting lubricants and other tableting aids such as magnesiumstearate and microcrystalline cellulose. In the case of capsules,tablets and pills, the dosage forms may also comprise buffering agents.Tablets and pills can additionally be prepared with enteric coatings andother release-controlling coatings.

Solid compositions of a similar type may also be employed as fillers insoft and hard-filled gelatin capsules using such excipients as lactoseor milk sugar as well as high molecular weight polyethylene glycols andthe like.

The compounds can also be in micro-encapsulated form with one or moreexcipients as noted above. The solid dosage forms of tablets, dragees,capsules, pills, and granules can be prepared with coatings and shellssuch as enteric coatings and other coatings well known in thepharmaceutical formulating art. They may optionally contain opacifyingagents and can also be of a composition that they release theingredient(s) only, or preferably, in a certain part of the intestinaltract, optionally in a delayed manner. Examples of embeddingcompositions which can be used include polymeric substances and waxes.

Dosage forms for topical or transdermal administration of a compound ofthis invention further include ointments, pastes, creams, lotions, gels,powders, solutions, sprays, inhalants, or patches. The active componentis admixed under sterile conditions with a pharmaceutically acceptablecarrier and any needed preservatives or buffers as may be required.Ophthalmic formulations, ear drops, eye ointments, powders and solutionsare also contemplated as being within the scope of this invention.

The ointments, pastes, creams and gels may contain, in addition to anactive compound of this invention, excipients such as animal andvegetable fats, oils, waxes, paraffins, starch, tragacanth, cellulosederivatives, polyethylene glycols, silicones, bentonites, silicic acid,talc and zinc oxide, or mixtures thereof.

Powders and sprays can contain, in addition to the active compounds ofthis invention, excipients such as lactose, talc, silicic acid, aluminumhydroxide, calcium silicates and polyamide powder, or mixtures of thesesubstances. Sprays can additionally contain customary propellants, suchas chlorofluorohydrocarbons.

Transdermal patches have the added advantage of providing controlleddelivery of active compound to the body. Such dosage forms can be madeby dissolving or dispersing the compound in the proper medium.Absorption enhancers can also be used to increase the flux of thecompound across the skin. The rate can be controlled by either providinga rate controlling membrane or by dispersing the compound in a polymermatrix or gel.

Accordingly, the compounds of the present invention are useful in thetreatment or alleviation of disease, especially those disorders relatedto neurological diseases or neurodegenerative disorders, such asAlzheimer's disease, Parkinson's disease, Lou Gehrig's disease, ormultiple sclerosis, to name a few, not to mention central or peripheralnervous system damage, dysfunction, or complications involving samestemming from edema, injury, or trauma. Such damage, dysfunction, orcomplications may be characterized by an apparent neurological,neurodegenerative, physiological, psychological, or behavioralaberrations, the symptoms of which can be reduced by the administrationof an effective amount of the active compounds of the present invention.

The following examples are provided for further illustration of thepresent invention, and do not limit the invention.

EXAMPLE 1 Synthesis of Compounds

General methods. In this example, the para-fluoro (TH-237A, TH-236B, andTH-OPEN) and para-trifluoromethyl (TH-242A, TH-242B, and TH-OPENTFM)compounds were synthesized based on methods for a small syntheticcompound as set forth in the scheme below. The ¹H, ¹³C NMR spectra wererecorded on a Bruker 400 (400 and 100 MHz respectively) spectrometer.High-resolution mass spectra (HRMS) were obtained on a VG instrument ZABdouble-focusing mass spectrometer. The IR spectra were recorded on aShimadzu FTIR 8400S instrument. Melting points were determined using aThomas-Hoover melting point apparatus and were uncorrected. Columnchromatography was performed employing silica gel (230-400mesh). X-raydiffraction data were collected on the Bruker instrument using BrukerAPEX ccd area detector with graphite-monochromated Mo Kα radiation(λ=0.71073 Å). The 4-fluorobenzaldehyde, tris(hydroxymethyl)aminomethaneand toluene were bought from Sigma-Aldrich., Milwaukee, Wis. Thecompound was dissolved in Captisol® (Cydex, Lenexa Kans.) for use in thebiological experiments.Synthetic Methods.

As an example, para-fluorinated compounds were prepared. Morespecifically, a suspension of 4-fluorobenzaldehyde (27 g, 0.22 mol) andtris(hydroxymethyl)aminomethane (13 g, 0.11 mol) in toluene (350 ml) washeated at reflux temperature with azeotropic removal of water for 12hours. The reaction mixture was concentrated, stirred at roomtemperature, and the precipitated, unreacted 4-fluorobenzaldehyde wasfiltered off. The residue obtained after removal of solvent wassubjected to flash chromatography on silica gel usinghexane:ethylacetate (4:1 and 1:1). Crystallization of the respectivefractions afforded pure compounds TH-237A, TH-236B, and TH-OPEN inyields 66%, 5%, and 21% respectively based on an equimolar productdistribution ratio. The structures of the products were assigned byspectral data and the relative stereochemistry of TH-237A was assignedfrom single crystal X-ray diffraction data. The ellipsoid drawing of themolecular structure TH-237A from X-ray diffraction study is shown inFIG. 1.

(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) (1)

Crystallized from hexane as white crystalline solid; mp. 90° C.; IR υ.cm⁻¹ 3444, 2873, 1606, 1504, 1222, 1153, 1078, 1006, 837; ¹H NMR (400MHz, CDCl₃) δ 3.50 (br s, 2H), 3.94 (d, J=8.9 Hz, 2H), 4.05 (d, J=8.9Hz, 2H), 5.55 (s, 2H), 7.07 (m, 4H), 7.44 m, 4H); ¹³C NMR (100 MHz,CDCl₃) δ 65.63, 72.66, 74.89, 96.65, 115.41, 115.58, 128.55, 128.62,135.26, 135.29, 161.95, 163.91; HRMS (FAB+) m/z calculated forC₁₈H₁₈NO₃F₂ [M+H] 334.1255 found 334.1230.

(3R,5R) and (3S,5S)(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-236B) (2)

Crystallized from hexane—methylene chloride as white crystalline solid;mp. 115° C.; IR υ. cm⁻¹ 3440, 2870, 1606, 1512, 1427, 1384, 1226, 1155,1076, 837; ¹H NMR (CDCl₃) δ 3.75 (m, 2H), 3.84 (d, J=8.8 Hz, 1H), 3.88(d, J=8.9Hz, 1H), 4.10 (d, J=8.9 Hz,1H), 4.20 (d, J=8.8 Hz, 1H), 5.16(s, 1H), 5.51 (s, 1H), 6.89 (m, 6H), 7.27 (m, 2H); ³C NMR (CDCl₃) δ65.60, 72.12, 74.87, 93.03, 93.91, 115.14, 115.31, 115.35, 115.52,115.78, 129.21, 129.29, 129.34, 129.42, 130.21, 130.24, 135.87, 135.90,161.89, 164.34; HRMS (FAB+) m/z calcd for C₁₈H₁₈NO₃F₂ [M+H] 334.1255found 334.1237.

(R/S)-(2-(4-fluorophenyl)oxazolidine-4,4-diyl)dimethanol (TH-OPEN) (3)

Crystallized from isopropanol as white crystalline solid; mp. 89° C.; IRυ. cm⁻¹ 3450, 2877, 1604, 1512, 1420, 1296, 1228, 1157, 1047, 837; ¹HNMR (CDCl₃) δ 3.58 (m, 3H), 3.71 (m, 2H), 3.85 (d, J=8.6 Hz, 1H), 5.41(s, 1H), 7.06 (m, 2H), 7.44 (m, 2H); ¹³C NMR (CDCl₃) δ 64.57, 64.98,67.62, 70.73, 91.79, 115.81, 116.02, 128.29, 128.37, 134.91, 162.17,164.63; HRMS (FAB+) m/z calcd for C₁₁H₁₅NO₃F [M+H] 228.1036 found228.1036.

As another example, para-trifluoro compounds were prepared. Synthesis ofpara-trifluoro analogs of was accomplished similar to the synthesis offluorinated compounds and purified by flash chromatography on silica gelusing hexane and ethyl acetate mixture. The products were obtained inyields 15%, 21% and 57% respectively based on equal product distributionratio.

((3R,5S,7as)-(3,5-bis(4-(trifluoromethyl)phenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A) (4)

Crystallized from hexane—methylene chloride as white crystalline solid;mp. 102° C.; IR υ. cm⁻¹ 3470, 2875, 1620, 1326, 1164, 1126, 1066, 1016,827; ¹H NMR (CDCl₃) δ 3.50 (br s, 2H), 3.94 (d, J=8.9 Hz, 2H), 4.05 (d,J=8.9 Hz, 2H), 5.55 (s, 2H), 7.07 (m, 2H), 7.44 (m, 2H); ¹³C NMR (CDCl₃)δ 65.98, 73.13, 75.45, 97.17, 123.01, 126.07, 126.10, 127.56, 130.89,131.21, 131.53, 131.85, 143.78; HRMS (FAB+) m/z calcd for C₂₀H₁₈NO₃F₆[M+H] 434.1191 found 434.1179. The relative stereochemistry wasdetermined by single crystal X-ray diffraction.

(3R,5R) and (3S,5S)(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242B) (5)

Crystallized from hexane—methylene chloride as white crystalline solid;mp. 120° C.; IR υ. cm⁻¹ 3470, 2875, 1622, 1480, 1427, 1384, 1310, 1218,1164, 1018, 836; ¹H NMR (CDCl₃) δ 3.73 (m, 2H), 3.84 (t, J=8.8 Hz, 1H),4.17 (d, J=8.9 Hz, 1H), 4.23 (d, J=8.9 Hz, 1H), 5.16 (s, 1H), 5.59 (s,1H), 7.08 (d, J=8.0 Hz, 2H), 7.27 (m, 6H); ¹³C NMR (CDCl₃) δ 65.47,72.55, 74.95, 75.01, 92.88, 93.77, 125.34, 125.38, 125.42, 125.45,125.49, 127.87, 127.96, 130.59, 130.92, 131.24, 131.56, 138.23, 143.77;HRMS (FAB+) m/z calcd for C₂₀H₁₈NO₃F₆ [M+H] 434.1191 found 434.1180. Therelative stereochemistry was determined by single crystal X-raydiffraction.

(R/S)-(2-(4-(trifluoromethyl)phenyl)oxazolidine-4,4-diyl)dimethanol(TH-OPENTFM) (6)

Crystallized from ethyl acetate as white crystalline solid; mp. 98° C.;IR υ. cm⁻¹ 3380, 2880, 1622, 1415, 1326, 1164, 1124, 1068, 1018, 839; ¹HNMR (CDCl₃) δ 3.64 (m, 5H), 3.86 (d, J=8.6 Hz, 1H), 5.50 (s, 1H), 7.63(m, 4H); ¹³C NMR (CDCl₃) δ. 64.54, 64.94, 67.69, 70.76, 91.55, 125.91,125.96, 126.89, 131.20, 131.51, 143.18; HRMS (FAB+) m/z calcd forC₁₂H₁₅NO₃F₂ [M+H] 278.1004 found 278.1002.

It will be readily appreciated to those skilled in the art thatmodification to the starting materials may be made in order to arrive atthe compounds of the present invention. For example, use of4-trifluoromethylbenzaldehyde, 4-difluoromethylbenzaldehyde,4-fluoromethylbenzaldehyde, 4-chlorobenzaldehyde,3-fluoromethylbenzaldehyde 3-trifluoromethylbenzaldehyde,3-difluoromethylbenzaldehyde, 3-fluoromethylbenzaldehyde,3-chlorobenzaldehyde 2-fluoromethylbenzaldehyde2-trifluoromethylbenzaldehyde, 2-difluoromethylbenzaldehyde,2-fluoromethylbenzaldehyde, 2-chlorobenzaldehyde and the like as thestarting material will result in the appropriate substitutions on thearomatic rings.

EXAMPLE 2 Neuroprotective Effect of Stereoisomers in Neuronal Cells inCulture after Exposure to Aβ peptides

This example illustrates the neuroprotective effects of TH-237A inneuronal cells after exposure to Aβ peptides. To prepare the primaryneurons, dissociated cortical cell cultures were established fromembryonic day 18 rat festuses recovered from pregnant Sprague Dawleyrats (Harlan Sprague Dawley, Inc., Indianapolis, Ind.) as describedpreviously (Michaelis et al., 1994). Pups were delivered by cesareansection while the dam was anesthetized with pentobarbital (140 mg/kg,i.p.), and the brains were recovered according to National Institutes ofHealth-approved protocols. After the final precipitation step, neuronswere suspended in fresh DMEM/F12 (Sigma Chemical Co. St. Louis, Mo.)with 10% fetal bovine serum (Atlanta Biologicals, Atlanta, Ga.) andplated at a density of 2.5×10⁵ cells in 35 mm glass bottom microwelldishes (Mat-Tek Co., Ashland, Mass.), coated with poly-D-lysine.Serum-containing medium was removed after 24 hours, and the cells weremaintained in serum-free DMEM/F12 containing the N₂ supplements.Cultures were grown at 37° C. in 5% CO₂ and 97% humidity as described(Michaelis et al., 1994).

After five days in culture, the primary neurons were exposed to eitherAβ₂₅₋₃₅ or Aβ₁₋₄₂ in the presence or absence of concentrations ofTH-237A ranging from 0.5 to 60 nM. The TH-237A was added about 2 hoursbefore the Aβ peptides. The Aβ₂₅₋₃₅ was synthesized and purified in theBiochemical Research Services Lab, University of Kansas. The reversesequence peptide used as a control, Aβ₃₅₋₂₅, and the Aβ₁₋₄₂ peptide usedin confirmatory experiments were purchased from Bachem (Torrance,Calif.). Prior to adding the peptides to the cultures, the Aβ peptidestocks (1.3 mg/ml in double-distilled H₂O) were diluted into 10 mMTris/Cl, pH 7.4, and maintained at about 37° C. for 24 hours. Each batchof Aβ peptide was analyzed for β-sheet formation by circular dichroism,but no effort was made to separate oligomers from fibrils. The peptideswere added directly to the culture medium, usually at 10 μM finalconcentration. Control cultures received the DMSO vehicle alone, and thefinal concentration of DMSO never exceeded 0.04%. Assays were carriedout 48 hours following Aβ peptide addition.

The effects of the Aβ peptides and TH-237A were primarily determined bymonitoring neuronal cell survival using the Live/Dead assay aspreviously described (Michaelis et al., 1998; Michaelis et al., 2005).Following the indicated periods of exposure to the peptides and/or thedrugs, cells were labeled with 20 μM propidium iodide (PI) and 150 nMcalcein acetoxy-methylester (Molecular Probes, Eugene, Oreg.) for 30minutes at 37° C. After incubation with the dyes, the dishes were rinsedwith phosphate-buffered saline (PBS) and placed on the stage of a Nikoninverted microscope (Nikon Eclipse TE200, Japan) with filters forfluorescein-isothiocyanate and Texas Red. Digital images were capturedwith a Dage camera and saved in Adobe Photoshop™. The number of viable(green) and dead (red) neurons was determined by counting the cells, andthis was done in 6-12 microscopic fields per vulture dish in duplicatedishes for each treatment. All experimental treatments were carried outon at least two separate embryonic neuronal preparations. Thus,approximately 1500 neurons were scored under each treatment condition.The fraction of viable cells in each field was calculated based on thetotal number of cells counted in each field. Raw data from eachexperiment were combined and the significance of differences betweencultures exposed to various treatments was determined using Student's ttest. Neuronal survival in the untreated control samples was consideredto represent maximal viability and that in the Aβ-only samples theminimal viability.

FIG. 2 illustrates that TH-237A protected the primary cortical neuronsexposed to the toxic Aβ₂₅₋₃₅ peptides. The EC₅₀ for TH-237A(concentration that lead to a 50% increase in neuronal survival in thepresence of the Aβ peptide) was 5 nM. Although the small toxic Aβ₂₅₋₃₅peptide was used in the majority of studies, the observations wereconfirmed with exposure to Aβ₁₋₄₂ peptides.

In addition, limited studies involving the racemic TH-236B and theTH-OPEN compound showed the EC₅₀ to be about 40 and 50 nM, respectively.Thus, TH-237A clearly exhibited higher neuroprotective effects in vitro.

It is interesting to note that oxazolidines may operate as prodrugs byundergoing hydrolysis in aqueous solutions. This explain in part whyTH-OPEN exhibits some degree of neuroprotection comparable to that ofTH-236B.

EXAMPLE 3 Neuroprotective Effect of TH-237A in Neuronal Cells in CultureAfter Exposure to Aβ Peptides

Because TH-237A was determined to be the most potent stereoisomer fromthe previous example, further studies were performed using thestereomerically pure compound. In this example, the effects ofneurotoxic stimuli other than Aβ peptides were used to assess protectionagainst various cell-death initiators. Primary neurons were prepared asdiscussed previously. In this example, staurosporine (100 nM) was usedto induce apoptosis, thapsigargin (100 nM) to cause ER stress, andparaquat (25 μM) or hydrogen peroxide (25 μM) to induce oxidativestress. All reagents were obtained from Sigma Chemical Co., St Louis,Mo.

TH-237A was added at 100 nM concentration about 2 hours before the toxicstimuli, and cell viability was determined using the Live/Dead assay andobtaining data from multiple fields as described above. The results areillustrated in FIG. 3. Clearly, TH-237A provided neuroprotection for theneuronal cells regardless of the source of the neurotoxic stimuli.

EXAMPLE 4 In Vitro Evaluation of Brain Uptake of Stereoisomers

In this example, the pharmacokinetic properties of TH-237A, racemicTH-236B, and TH-OPEN were investigated for uptake into the brain. Twodifferent methodologies, a rhodamine assay and radiolabeling, were used.

Example 4A Rhodamine Assay

First, a rhodamine 123 assay was used for to assess uptake of the testcompound in brain endothelial cells. Bovine brain microvesselendothelial cells (“BBMECs”) were isolated and grown in primary cultureon 12 well cluster dishes at a density of 50,000 cells/cm² essentiallyas described previously (Rice et al., 2005). The culture medium waschanged every other day after seeding until a confluent monolayer wasformed as determined by light microscopy. Experiments were performed inphosphate buffered saltine supplemented with calcium and glucose (PBSA),pH 7.4. Briefly, the growth medium was first aspirated off, and thecells were rinsed three times with pre-warmed (37° C.) PBSA. Themonolayers were then equilibrated either in 1 ml PBSA for 1 hour at 37°C. for control experiments or equilibrated for 30 minutes in PBSA alone,followed by another 45 minutes pre-incubation with the TH-237A.Cyclosporin A (CsA; 10 μM) was used as a known P-glycoprotein inhibitorand as the positive control. Rhodamine 123 accumulation was allowed toproceed for 45 minutes with or without a potential inhibitor presentwith gentile agitation (about 30 rpm) at 37° C. At the end of theexperiment, the drug solution was removed by aspiration and themonolayers were immediately rinsed three times with ice-cold PBSA. Eachmonolayer was solubilized for 30 minutes (37° C.) with 1 ml of lysingsolution (0.5% v/v Triton X-100 in 0.2 N NaOH). Cell lysates wereassayed using a microplate fluorescence reader (Bio-Tek Instruments,Winooski, Vt.) at excitation/emission wavelengths of 485 nm/520 nm, thenquantified against standard curves of rhodamine 123 in lysing solution.The fluorescence of the cell lysates was corrected for autofluorescenceof untreated cells. The protein content of each monolayer was thendetermined using the BCA protein assay reagent kit. Results wereexpressed as total nanomoles of rhodamine 123 accumulation per mgcellular protein for agents tested at 10 μM. Agent Rhodamine uptake(nmol/mg protein) TH-237A 0.21 TH-236B (racemic) 0.23 TH-OPEN 0.27

The absence of an effect of the TH-237A on rhodamine 123 accumulationindicates the compound is not a substrate for the P-glycoprotein effluxtransporter and thus is likely to cross the blood brain barrier.Similarly, racemic TH-236B and TH-OPEN showed the absence of rhodamine123 accumulation.

In a separate experiment, a trifluromethyl derivative (TH-OPEN) wasinvestigated. This compound had a rhodamine updake of 0.3 nmol/mgprotein. Because pharmaceuticals that have little likelihood of enteringthe brain (e.g. paclitaxel) have rhodamine uptake values of 0.8 or more,the stereoisomers are likely to cross the blood brain barrier.

Example 4B Radiolabeling Experiments

In a separate experiment, the permeation of TH-237A across BBMECmonolayers was demonstrated. The BBMECs were grown on 0.4 μmpolycarbonate membranes. After they reached confluency, the cells weretransferred to side-by-side diffusion chambers to characterize thetransport of radiolabeled TH-237A and Taxol (paclitaxel) across themonolayer. The TH-237A was custom labeled with tritium [³H] by MoravekBiochemicals, Inc. (Brea, Calif.). Transport studies were performed inpH 7.4 standard buffer solutions, consisting of either Hank's balancedsalt solution (HBSS) or phosphate buffered saline (PBS) supplementedwith 0.63 mM CaCl₂, 0.74 mM MgSO₄, 5.3 mM glucose and 0.1 mM ascorbicacid (PBSA). Briefly, all studies were performed in 3 ml of PBSA in eachdonor and receiver chamber of the side-by-side diffusion chambers andstirred at 600 rpm at 37° C. The cells were allowed to equilibrate inPBSA for 30 minutes prior to each experiment and oriented such thatapical or blood side of the cells face the donor chamber and thebasolateral or brain side of the cells adhere to the polycarbonatemembranes and face the receiver chamber of the diffusion apparatus. Ateach time point, a 100 μl sample was taken from the receiver compartmentand immediately replaced with an equal volume of PBSA. The transportstudies were performed in the presence or absence of CsA (5-10 μM).Monolayers were checked for trypan blue exclusion after experiments aswell to assess general cell viability. The permeability of allmonolayers used in these experiments was monitored for [¹⁴C] sucroseleakage as a measure of potential TH-237A-induced loss of integrity. Theradioactivity was quantified using liquid scintillation spectrometry.Apparent permeability coefficients (P_(app)) were calculated as 0.5×10⁻⁵cm/sec for Taxol (paclitaxel), and 27×10⁻⁵ cm/sec for TH-237A.

EXAMPLE 4 In Vivo Pharmacokinetic Evaluation of TH-237A in Plasma andBrain

In this example, the pharmacokinetics of TH-237A were evaluated in vivo.Male Balb/C mice were dosed with TH-237A (10 mg/Kg in Captisol®) viaeither an i.v. injection into the tail vein or via subcutaneous (sc)injection. At multiple time points ranging from 0 to 240 minutes, 12mice (n=6, i.v.; n=6, s.c.) were anesthetized with isoflurane, and bloodwas collected via cardiac puncture. Mice were perfused with 30 mL ofsaline to wash remaining blood from the vessels, and the brain tissuewas harvested. The levels of TH-237A in plasma and brain were quantifiedusing mass spectrometric methods.

Sample preparations. Brain homogenate was prepared in a 1:4 ratio withdeionized water. A sonic dismembrator was pulsed at 30% power until thesample was liquified. Aliquots of mouse plasma (0.05 mL) or mouse brainhomogenates (0.25 g) were spiked with 50 ng of internal standard(deuterated TH-237A) and vortexed for 10 seconds. The TH-237A andinternal standard were extracted using 1.3 mL of methyl t-butyl ether.Samples were vortexed for 5 minutes and centrifuged. The supernatant wastransferred to 2 mL centrifuge tubes and evaporated to dryness. Thesample was reconstituted in 0.2 mL of sample solvent, vortexed andcentrifuged before a 10 uL aliquot was injected on to the LC/MS systemfor analysis.

Analysis of TH-237A. The levels of the drug in the samples weredetermined by means of HPLC/MS. The column was a Gemini-C18, 50×2 mm(Phenomenex, catalogue number 00B-4435-B0, serial number 265528-1). Themobile phase A was 100:0.1 deionized water/formic acid, and the mobilephase B was 20:80:0.1 methanol/acetonitrile/formic acid. Elution wasperformed using isocratic flow with 47% mobile phase B for 5.5 minutes.The column was rinsed at 80% B at the end of each run and thenre-equilibrated at 47%. The flow rate was 0.22 mL/min. The effluent forthe first two minutes was diverted to waste. The retention time was 4.5minutes. The instrument used for the analyses of TH-237A is a ShimadzuLC/MS 2010 system (single quadrapole mass spectrometer used inelectrospray positive mode). The results are illustrated in FIG. 4. Theplasma levels (ng/mL) of TH-237A over time following administration byeither i.v. injection (filled squares) or subcutaneously (open squares)are indicated on the left axis. The brain concentrations of TH-237A(ng/gm) following administration by either i.v. injection (filledcircles) or subcutaneously (open circles) are indicated on the rightaxis. The results of these experiments show that a very significantamount of the drug enters the plasma regardless of route ofadministration and exhibits a relatively long half-life, on the order ofhours. In addition, relatively high brain concentrations of the drug areachieved quite rapidly, and brain levels of approximately 300 nM TH-237Aare still present at 4 hours, suggesting the drug is only slowly lostfrom the brain over time.

EXAMPLE 5 Assessment of TH-237A on Cell Proliferation

In this example, the cytotoxic effects of TH-237A on proliferating cellswas investigated using pacitaxel as comparative test compound. MCF-7human breast cancer and B16 murine melanoma cells in Dulbecco's MEM/F12medium containing 5% fetal calf serum were plated in 96-well cultureplates at a density of 2000 cells per well. After a 24 hours incubationat 37° C. the medium was removed and replaced with fresh mediumcontaining either paclitaxel (Taxol) or TH-237A at varyingconcentrations ranging between 31 μM and 500 μM. The plates wereincubated for 72 hours and the degree of proliferation was measured bystaining with sulforhodamine B. The ED₅₀ values were obtained byplotting the absorbance at 570 nm against the concentration of thecompounds. Taxol had an ED₅₀ of 8.7 nM and 2.9 nM in B16 and MCF7 cells,respectively. The ED₅₀ of TH-237A was much higher—about 5.5 μM and 12.3μM in B16 and MCF7 cells. Thus, TH-237A does not have any of the markettoxic effects that Taxol has on dividing cells.

A similar experiment was performed on TH-237A, TH-236B, and TH-OPEN on acancer cell line that over-expresses the drug transporter P-glycoprotein(MCF 7-adr cells). These cells become considerably less sensitive to thedrugs because they can pump them out so effectively. The results areshown in the following Table 1: TABLE 1 Cytotoxicity Assay in MCF 7-adrCells Taxol (paclitaxel)  1.2 μM TH-237A  44 μM TH-236B (racemic) 110 μMTH-OPEN 130 μM

Clearly, Taxol is not readily taken up into these MCF 7-adr cells, butthe compounds of the present invention are even less permeable inreaching concentrations that can inhibit proliferation. Further, TH-237Adoes seem to move past the P-glycoprotein transporter more readily thanthe other two compounds, but very high concentrations of the compoundsare required to affect the cell proliferation significantly.

EXAMPLE 6 Investigation of Microtubule-Stabilizing Properties of TH-237A

In this example, the mechanism of TH-237A's neuroprotective effects wasinvestigated. In a first experiment, the microtubule-stabilizing abilityof TH-237A was investigated using a tubulin assembly centrifugationassay. Tubulin (1.0 mg/ml), free of microtubule-associated proteins(“MAPs”), was incubated in PEM buffer (0.1 M Pipes, 1 mM EGTA, 1 mMMgSO₄, pH 6.9), 4% DMSO, various concentrations of paclitaxel orTH-237A, with or without 0.5 mM GTP, in a total volume of 0.1 ml for 15minutes at 37° C. Samples were centrifuged at 50,000×g for 4 minutes ina Beckman TL-100 ultracentrifuge. Protein determinations were performedon the supernatants and the amount of polymer formed was calculated fromthe difference between the starting concentration and the supernatantconcentration. The maximum concentration of polymer was taken to be thatformed at 25 μM paclitaxel. An experiment was also done using a tubulinpreparation containing microtubule-associated proteins (“MTP”) at aprotein concentration of 2 mg/ml without GTP. The results showed that75% of tubulin polymerized at 1.0 μM of Taxol, but only 10% of tublinpolymerized at 200 μM of TH-237A.

A multi-well plate assay was then performed. This assay depends on theincrease in fluorescence when 4′,6-diamidino-2-phenylindole (DAPI) bindsto microtubules. MTP at 2 mg/ml was used in the absence of GTP and inthe presence of 10 μM DAPI. Assays were done in 96-well plates in a 0.1ml volume. The plates were incubated at 37° C. for 30 minutes afterwhich fluorescence was read on a fluorescence plate reader using anexcitation wavelength of 360 nm and an emission wavelength of 460 nm. Inthe multi-well plate assay, Taxol® was consistently two orders ofmagnitude more potent than TH-237A in promoting tubulin polymerization.

In another experiment, the cold stability of microtubles wasinvestigated. Microtubules were formed from MAP-free tubulin (2 mg/ml)and MTP (2 mg/ml) at 37° C. A sample was centrifuged at 50,000×g todetermine the amount of polymer formed. To three other samples DMSO, 20μM paclitaxel or 400 μM TH-237A was added, and the samples were placedon ice for 15 minutes before centrifuging at 4° C. Pellets weredissolved in 0.1 ml of 0.1 M NaOH and protein determinations were madeon the supernatants and pellets. Cold-induced depolymerization leads toan increase in the supernatant protein concentration. When TH-237A wascompared with Taxol in assessing the cold stability of microtubules,Taxol® prevented cold-induced depolymerization of nearly 100% of themicrotubules at a concentration of 25 μM, whereas concentrations ofTH-237A as high as 400 μM prevented only about 10% of the cold-induceddepolymerization of the microtubules.

EXAMPLE 7 Interaction of TH-237A with Microtubules

Binding of ³H-TH-237A to microtubules—Microtubules were formed from MTP(2 mg/ml) or from tubulin depleted of MAPs (3 mg/ml) in the presence of0.5 mM GTP. Various concentrations of either [³H]-paclitaxel or[³H]-TH-237A in a 4 μl volume were added to separate 96 μl aliquotportions of the microtubule suspension. After 10 minutes at 37° C., themicrotubules were collected by centrifugation and dissolved in 0.1 ml of0.1 M NaOH. Protein and radioactivity determinations of the dissolvedmicrotubules were performed.

The radiolabeled TH-237A did bind to the microtubules. However, itrequired 10 times more TH-237A than Taxol® to achieve a maximal bindinglevel. This indicates that the agent only binds to microtubules at veryhigh concentrations at which non-specific interactions may be occurring.

Competitive binding of paclitaxel and TH-237A—Microtubules were formedfrom MTP (2 mg/ml) in the presence of 0.5 mM GTP. [³H]-Paclitaxel (4 μl)was added to separate 92 μl aliquot portions of the microtubulesuspension, followed by 4 μl aliquot portions of TH-237A solutions. Thefinal concentration of paclitaxel was 20 μM and the TH-237Aconcentration ranged from 100 to 400 μM. After 10 minutes at 37° C., themicrotubules were collected by centrifugation and dissolved in 0.1 ml of0.1 M NaOH. Protein and radioactivity determinations of the dissolvedmicrotubules were performed.

In the competitive binding assays, very little competition was observedin the displacement of labeled Taxol® (20 μM) by TH-237A, about 15% at aTH-237A concentration of 400 μM. Similarly, when the binding of labeledTH-237A to microtubules was measured at 100 μM concentration, additionof 40 μM Taxol® led to displacement of only about 5% of the boundTH-237A. These data indicate that the two agents do not compete forbinding to the same sites on microtubules.

Immunostaining of cellular microtubules—Cells were grown in monolayer onsterile slide cover slips in a 6-well plate and treated with paclitaxelor TH-237A for different periods of time. The cover slips were washedwith phosphate-buffered saline and the cells fixed by treatment with 95%EtOH at −20° C. for 30 minutes. The cover slips were placed in ahumidified chamber and treated with the primary antibody (a mouseanti-β-tubulin monoclonal antibody) for 2 hours to overnight at roomtemperature. This was followed by washing with phosphate-buffered salineand treatment with the secondary antibody (FITC goat anti-mouse) for 1hour at room temperature. Cover slips were examined on a Nikon Optiphotfluorescence microscope.

The polymerization of the microtubules in situ in the cells was clearlyevident at 1 and 10 μM Taxol®. No such stabilization was observed in thecells treated with either 50 or 100 μM TH-237A. These observationsfurther indicate TH-237A does not lead to stabilization of themicrotubules network in intact cells in the concentration range that ledto neuroprotection.

EXAMPLE 9 In Vivo Analysis of TH-237A Treatment in Tau-Mutant Mice

In this example, the in vivo effects of TH-237A in tau-mutant mice wereinvestigated. More specifically, three groups of mice with the P301L taumutation were as follows: (1) +Tau, mutant mice which had unrestrictedaccess to food and were administered vehicle only, (2) Tau/FR, mutantmice with food restriction (85% of free feed weight), and vehicle only,and (3) Tau/FR/Drug, mutant mice with food restriction (85% of free feedweight), 10 mg/kg of TH-237A (sc administration) daily for 15 weeks. Thetreatments (FR or FR/drug) were begun at about 5.5 months of age. At 9.5months, treatment was terminated and the animals were sacrificed. Forthe +tau mice, severe motor pathology developed, and the mice weresacrificed at about 8.5 months.

To evaluate the effect of TH-237A on pathology, biochemical indicatorsof abnormal tau were investigated using immunoblot and densitometery.Three antibodies that selectively react with hyper-phosphorylatedinsoluble tau were used, CP13, PHF1, and AT8. The mouse brains andspinal cords were recovered, subfractionated, and the sarkosyl-insolubleP3 fractions were isolated and run on SDS-PAGE followed by immunoblotanalysis. The 64 kDa abnormal tau band was labeled using the antibodiesas shown in FIG. 5. The relative results of the antibody labeling areshown in FIGS. 6(a)-(c) for the brain and FIG. 7(a)-(c) for the spinalcord. As expected, the +Tau mice showed strong P3 labeling with allthree antibodies to the abnormal tau. The tau mutant mice on foodrestriction did not develop motor pathology prior to sacrifice at age9.5 months. The tau mutant mice on food restriction also had less brainand spinal cord labeling of abnormal tau when sacrificed. The tau mutantmice on food restriction given the TH-237A did not develop motorpathology, but showed significantly less labeling of abnormal tau thatthe FR-only mice. Thus, although food restriction slowed the appearanceof motor, spinal cord, and brain pathology, chronic treatment withTH-237A slowed the disease progression even more significantly. Thus,this experiment suggests an in vivo neuroprotective effect associatedwith TH-237A.

REFERENCES CITED

The publications and other materials used herein to illuminate thebackground of the invention or provide additional details respecting thepractice, are incorporated by reference.

Burr et al, Prodrugs as drug delivery systems 66. Hydrolysis of variousoxazolidines and N-acylated oxazolidines—potential prodrug types forβ-aminoalcohols or carbonyl containing drugs, Arch. Pharm. Chem., Sci.Ed. (1987), 15, 76-86.

Michaelis M L, Walsh J L, Pal R, Hurlbert M, Hoel G, Bland K, Foye J,Kwong WH (1994) Immunologic localization and kinetic characterization ofa Na+/Ca2+ exchanger in neuronal and non-neuronal cells, Brain Res661:104-116.

Michaelis M L, Ranciat N, Chen Y, Bechtel M, Ragan R, Hepperle M, Liu Y,Georg G (1998) Protection against beta-amyloid toxicity in primaryneurons by paclitaxel (Taxol), J Neurochem 70:1623-1627.

Michaelis M L, Ansar S, Chen Y, Reiff E R, Seyb K I, Himes R H, Audus KL, Georg G I (2005) Beta-Amyloid-induced neurodegeneration andprotection by structurally diverse microtubule-stabilizing agents, JPharmacol Exp Ther 312:659-668.

Rice A, Liu Y, Michaelis M L, Himes R H, Georg G I, Audus K L (2005)Chemical modification of paclitaxel (Taxol) reduces P-glycoproteininteractions and increases permeation across the blood-brain barrier invitro and in situ, J Med Chem 48:832-838.

Shintani Y, Tanaka T, Nozaki Y (1997) GS-164, a small syntheticcompound, stimulates tubulin polymerization by a similar mechanism tothat of Taxol, Cancer Chemother Pharmacol 40:513-520.

Shintani et al., Pharmaceutical compositions, microtubule polymerizationaccelerators, cell proliferation inhibitors, and antitumour agentscontaining 3,7-dioxa-1-azabicyclo[3,3,0]octane, Japan Patent JP 08325147(1996).

From the foregoing it will be seen that this invention is one welladapted to attain all ends and objectives herein-above set forth,together with the other advantages which are obvious and which areinherent to the invention. Further, since many possible embodiments maybe made of the invention without departing from the scope thereof, it isto be understood that all matters herein set forth are to be interpretedas illustrative, and not in a limiting sense. While specific embodimentshave been shown and discussed, various modifications may of course bemade, and the invention is not limited to the specific forms orarrangement of parts and steps described herein, except insofar as suchlimitations are included in the following claims. Further, it will beunderstood that certain features and subcombinations are of utility andmay be employed without reference to other features and subcombinations.This is contemplated by and is within the scope of the claims.

1. A stereomerically pure compound according to Formula I:

wherein A and B are sulfur or oxygen; wherein R₁ and R₂ areindependently halogen, alkyl, alkoxy, haloalkyl; and wherein R₃ isalcohol.
 2. The stereomerically pure compound according to Formula I ofclaim 1 wherein A and B are both oxygen, and wherein R₁ and R₂ are bothin the para position according to:

wherein R₁ and R₂ are independently halogen, alkyl, alkoxy, haloalkyl;and wherein R₃ is alcohol.
 3. The stereomerically pure compoundaccording to claim 2 which is selected from(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A);(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A);(3R,5S,7as)-(3,5-bis(4-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(4-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(4-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.4. The stereomerically pure compound according to Formula I of claim 1wherein A and B are both oxygen, and R₁ and R₂ are both in the metaposition.
 5. The stereomerically pure compound according to claim 4which is selected from(3R,5S,7as)-(3,5-bis(3-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(3-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(3-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(3-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.6. The stereomerically pure compound according to Formula I of claim 1wherein A and B are both oxygen, and R₁ and R₂ are both in the orthoposition.
 7. A stereomerically pure compound according to claim 6 whichis selected from(3R,5S,7as)-(3,5-bis(2-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol;(3R,5S,7as)-(3,5-bis(2-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-difluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-fluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-chlorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;(3R,5S,7as)-(3,5-bis(2-methylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol;and(3R,5S,7as)-(3,5-bis(2-methoxyphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)ethanol.8. The stereomerically pure compound according to Formula I of claim 1wherein A and B are both oxygen, and R₁ and R₂ are independently in thepara position, meta position, and ortho position, but R₁ and R₂ are notboth para, both meta, or both ortho.
 9. A method of a treating aneurodegenerative disorder in a patient comprising administering to apatient in need of such treatment a therapeutically effective amount ofstereomerically pure compound according to Formula I:

wherein A and B are sulfur or oxygen; wherein R₁ and R₂ areindependently halogen, alkyl, alkoxy, haloalkyl; and wherein R₃ isalcohol.
 10. The method of claim 9 wherein the stereomerically purecompound is(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) or a pharmaceutically acceptable prodrug thereof.
 11. Themethod of claim 10 wherein said stereomerically pure(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) is administered parenterally, transdermally, mucosally,nasally, buccally, sublingually, or orally.
 12. The method of claim 10wherein said stereomerically pure(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-237A) is complexed with a cyclodextran as a pharmaceuticallyacceptable carrier.
 13. The method of claim 9 neurodegenerative disorderis an amyloidosis disorder.
 14. The method of claim 9 wherein theneurodegenerative disorder is Alzheimer's.
 15. The method of claim 9wherein the patient is a mammal.
 16. The method of claim 9 wherein thetherapeutically effective amount is from about 1 to 100 mg/kg per day.17. The method of claim 9 wherein the stereomerically pure compound is(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A) or a pharmaceutically acceptable prodrug thereof.
 18. Themethod of claim 9 wherein said stereomerically pure compound does notstabilize microtubules.
 19. A pharmaceutical composition comprisingstereomerically pure compound according Formula I and a pharmaceuticallyacceptable carrier

wherein A and B are sulfur or oxygen; wherein R₁ and R₂ areindependently halogen, alkyl, alkoxy, haloalkyl; and wherein R₃ isalcohol.
 20. The pharmaceutical composition of claim 19 wherein thestereomerically pure compound is(3R,5S,7as)-(3,5-bis(4-fluorophenyl)tetrahydro-1H-oxazolo[3,4]-oxazol-7a-yl)methanol(TH-237A) or(3R,5S,7as)-(3,5bis(4-trifluoromethylphenyl)tetrahydro-1H-oxazolo[3,4-c]oxazol-7a-yl)methanol(TH-242A).
 21. The pharmaceutical composition of claim 19 wherein thecarrier is a cyclodextrin.